U.S. patent application number 12/155389 was filed with the patent office on 2009-04-23 for image display apparatus.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Toshiaki Kusunoki, Mutsumi Suzuki.
Application Number | 20090102376 12/155389 |
Document ID | / |
Family ID | 40562799 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090102376 |
Kind Code |
A1 |
Suzuki; Mutsumi ; et
al. |
April 23, 2009 |
Image display apparatus
Abstract
Degradation of an electron emission element by irradiation of
the positive ion generated inside a panel is suppressed. A
deflection electrode is periodically disposed, and the electron
emission region of an electron emission element is disposed so as
not to include a center line between adjacent deflection
electrodes, so that an electron beam trajectory is deflected and
bombardment or irradiation of the generated positive ion to the
electron emission region is prevented.
Inventors: |
Suzuki; Mutsumi; (Kodaira,
JP) ; Kusunoki; Toshiaki; (Tokorozawa, JP) |
Correspondence
Address: |
Stanley P. Fisher;Reed Smith LLP
Suite 1400, 3110 Fairview Park Drive
Falls Church
VA
22042-4503
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
40562799 |
Appl. No.: |
12/155389 |
Filed: |
June 3, 2008 |
Current U.S.
Class: |
313/505 |
Current CPC
Class: |
H01J 29/04 20130101;
H01J 2329/0486 20130101; H01J 31/127 20130101 |
Class at
Publication: |
313/505 |
International
Class: |
H01J 1/62 20060101
H01J001/62 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2007 |
JP |
JP2007-270027 |
Claims
1. An image display apparatus, comprising a display panel having a
cathode plate and a phosphor plate, and a drive circuit, wherein
the cathode plate comprises a plurality of electron emission
elements, a plurality of scan lines mutually in parallel, and a
plurality of data lines mutually in parallel and orthogonal to the
scan lines, the electron emission element is a thin film electron
emitter, in which a top electrode, an electron acceleration layer,
and a base electrode are provided, and a part of the top electrode
constitutes an electron emission region, and by applying a voltage
between the top electrode and the base electrode, electrons are
emitted from the electron emission region, the cathode plate
comprises a plurality of deflection electrodes, and has a center
line at a position dividing a distance between the inner edges of
adjacent the deflection electrodes in two equal parts, the electron
emission region is disposed so as not to include the center
line.
2. The image display apparatus according to claim 1, wherein a
height of the deflection electrode is higher than that of the
electron emission region.
3. The image display apparatus according to claim 1, wherein a
height of the highest region of the deflection electrode is
disposed at a position higher than a height of the highest region
of the electron emission region by 2 .mu.m or more.
4. The image display apparatus according to claim 1, wherein the
deflection electrode is disposed by a period of sub pixel of a
color-image display.
5. The image display apparatus according to claim 1, wherein the
deflection electrode is periodically disposed along an axis of the
direction in parallel with the scan line.
6. The image display apparatus according to claim 1, wherein the
deflection electrode is periodically disposed along an axis of the
direction in parallel with the data line.
7. The image display apparatus according to claim 1, wherein the
deflection electrode is electrically connected to the scan
line.
8. The image display apparatus according to claim 1, wherein the
deflection electrode is made of the same material as that of the
scan line.
9. The image display apparatus according to claim 1, wherein the
cathode plate comprises a contact electrode, wherein the contact
electrode is electrically connected to the scan line, and moreover,
is electrically connected to the top electrode, and at the same
time, is disposed along a side of the longer side from among the
sides constituting the electron emission region.
10. The image display apparatus according to claim 1, comprising a
constitution in which a deflection pulse is applied to a scan line
adjacent to the electron emission element connected to the selected
scan line in a period applying a scan pulse to the selected scan
line from among the plurality of scan lines.
11. The image display apparatus according to claim 10, wherein
assuming that, from among the voltages applied to the scan line
from the drive circuit, a voltage of the scan pulse is Vs, a
voltage applied to a non-selected scan line is Vns, and a voltage
of the deflection pulse is Vdef, the absolute value of (Vs-Vdef) is
larger than the absolute value of (Vs-Vns).
12. The image display apparatus according to claim 1, wherein the
phosphor plate comprises a phosphor and an acceleration electrode,
and is constituted so as to display an image by allowing the
emitted electron to excite the phosphor to emit light, the phosphor
plate comprises a phosphor region in which the phosphor is
patterned, and a center line of the phosphor region and a center
line of the electron emission region are disposed to be shifted to
each other.
13. The image display apparatus according to claim 1, wherein the
phosphor plate comprises the phosphor and the acceleration
electrode, and is constituted so as to display an image by allowing
the emitted electron to excite the phosphor to emit light, wherein,
in a projected plane projecting a component on the phosphor plate
and a component on the cathode plate, the electron emission region
is disposed so as not to be superposed with a region formed with
the phosphor.
14. The image display apparatus according to claim 1, wherein the
phosphor plate comprises the phosphor, a black matrix and the
acceleration electrode, and is constituted so as to display an
image by allowing the emitted electron to excite the phosphor to
emit light, and wherein, in a projected plane projecting a
component on the phosphor plate and a component on the cathode
plate, the electron emission region is disposed so as to be
included in the black matrix.
15. An image display apparatus comprising a display panel having a
cathode plate and a phosphor plate, and a drive circuit, wherein
the cathode plate comprises a plurality of electron emission
elements, a plurality of scan lines mutually in parallel, and a
plurality of data lines mutually in parallel and orthogonal to the
scan lines, the electron emission element is a thin film electron
emitter, in which a top electrode, an electron acceleration layer,
and a base electrode are provided, and a part of the top electrode
constitutes an electron emission region, and by applying a voltage
between the top electrode and the base electrode, electrons are
emitted from the electron emission region, a shield electrode is
provided between the electron emission region and the phosphor
plate, and wherein, in a projected plane projecting a pattern of
the electron emission region and a pattern of the shield electrode,
the electron emission region is disposed so as to be included in
the shield electrode.
16. An image display apparatus comprising a display panel having a
cathode plate and a phosphor plate, and a drive circuit, wherein
the cathode plate comprises a plurality of electron emission
elements, a plurality of scan lines mutually in parallel, and a
plurality of data lines mutually in parallel and orthogonal to the
scan lines, the electron emission element comprises a first
electrode and a second electrode, and the first electrode is
electrically connected to the scan line, and the second electrode
is electrically connected to the data line, the electron emission
element comprises an electron emission region, and when a voltage
is applied between the first electrode and the second electrode,
electrons are emitted from the electron emission region, the
phosphor plate comprises a phosphor and an acceleration electrode,
and is constituted so as to display an image by allowing the
emitted electron to excite the phosphor to emit light, and wherein,
in a projected plane projecting a component on the phosphor plate
and a component on the cathode plate, the electron emission region
is disposed so as not to be superposed with a region formed with
the phosphor.
17. The image display apparatus according to claim 16, wherein the
phosphor plate comprises a black matrix in addition to the phosphor
and the acceleration electrode, and wherein, in a projected plane
projecting a component on the phosphor plate and a component on the
cathode plate, the electron emission region is disposed so as to be
included in the black matrix.
18. The image display apparatus according to claim 16, wherein the
electron emission element is a thin film electron emitter, in which
a top electrode, an electron acceleration layer, and a base
electrode are provided, and a part of the top electrode constitutes
the electron emission region, and by applying a voltage between the
top electrode and the base electrode, electrons are emitted from
the electron emission region.
19. The image display apparatus according to claim 17, wherein the
electron emission element is a thin film electron emitter, in which
a top electrode, an electron acceleration layer, and a base
electrode are provided, and a part of the top electrode constitutes
the electron emission region, and by applying a voltage between the
top electrode and the base electrode, electrons are emitted from
the electron emission region.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority from Japanese Patent
Application No. JP 2007-270027 filed on Oct. 17, 2007, the content
of which is hereby incorporated by reference into this
application.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates to an image display apparatus
for displaying an image by using an electron emission element and a
phosphor disposed in a matrix-form.
BACKGROUND OF THE INVENTION
[0003] An image display device referred to also as a matrix
electron emitter display takes an intersection of electrode groups
orthogonal to each other as a pixel, and provides an electron
emission element on each pixel, and by adjusting an applied voltage
(amplitude of applied voltage) or a pulse width of an applied
voltage pulse to each electron emission element, amount of emitted
electrons is adjusted, and the emitted electrons are accelerated in
vacuum, and after that, and bombarded onto or irradiated at the
phosphor, thereby to allow the phosphor of the bombarded portion to
emit light. As the electron emission elements, there are those such
as using a field emission type cathode, a MIM
(Metal-Insulator-Metal) cathode, a carbon-nanotube cathode, a
diamond cathode, a surface conduction electron emitter element, a
ballistic electron surface-emitting cathode, and the like. Thus,
the matrix electron emitter display denotes a cathode luminescent
flat-panel display that combines the electron emission element and
the phosphor.
[0004] FIG. 1 is a schematic view showing a cross section of the
matrix electron emitter display. As shown in FIG. 1, in the matrix
electron emitter display, a cathode plate 601 disposed with the
electron emission-element and a phosphor plate 602 formed with a
phosphor are disposed facing with each other. In order that the
electron emitted from an electron emission element 301 reaches the
phosphor plate to excite the phosphor to emit light, a space
surrounded by the cathode plate, the phosphor plate, and a frame
component 603 is kept vacuum. To withstand the atmosphere pressure
from the outside, a spacer (support) 60 is inserted between the
cathode plate and the phosphor plate.
[0005] The phosphor plate 602 includes an acceleration electrode
122, and the acceleration electrode 122 is applied with high
voltage of approximately 3 KV to 12 KV. The electrons emitted from
the electron emission element 301 are accelerated by this high
voltage, and after that, are bombarded onto or irradiated at the
phosphor, thereby exciting the phosphor to emit light.
[0006] The electron emission element used for the matrix electron
emitter display includes a thin film electron emitter. The thin
film electron emitter has a structure laminating a top electrode,
an electron acceleration layer, and a base electrode, and includes
a MIM (Metal-Insulator-Metal) cathode, a MOS
(Metal-Oxide-Semiconductor) type cathode, a ballistic electron
surface-emitting cathode, a HEED (High-Efficiency Electron Emission
Device) type cathode, and the like. The structure of the MIM
cathode is, for example, described in Japanese Patent Application
Laid-Open Publication No. 2004-363075 (Patent Document 1). The MOS
type cathode uses a stacked film comprising of semiconductor and
insulator for the electron acceleration layer, and for example, is
described in Japanese Journal of Applied Physics, Vol. 36, Part 2,
No. 7B, pp. L939-L941 (1997) (Non-Patent Document 1). The ballistic
electron surface-emitting cathode uses porous silicon and the like
for the electron acceleration layer, and for example, is described
in Japanese Journal of Applied Physics, Vol. 34, Part 2, No. 6A,
pp. L705-L707 (1995) (Non-Patent Document 2). The thin film
electron emitter emits the electron accelerated in the electron
acceleration layer into vacuum. Further, the MIM cathode uses a
metal for the top electrode and the base electrode, and uses an
insulator for the electron acceleration layer, and for example, is
described in IEEE Transactions on Electron Devices, Vol. 49, No. 6,
pp. 1059-1065 (2002) (Non-Patent Document 3). The HEED type cathode
uses a stacked layer of silicon (Si) and SiO.sub.2 for the electron
acceleration layer, and for example, is described in Journal of
Vacuum Science and Technologies, B, vol. 23, No. 2 (2005), pp.
682-686 (Non-Patent Document 5).
[0007] FIG. 2 is an energy band diagram showing an operation
principle of the thin film electron emitter. A base electrode 13,
an electron acceleration layer 12, and a top electrode 11 are
stacked, and a state when a plus voltage is applied to the top
electrode 11 is illustrated. In the case of the MIM cathode, as the
electron acceleration layer 12, an insulator is used. By the
voltage applied between the top electrode and the base electrode,
an electric field is generated inside the electron acceleration
layer 12. By this electric field, an electron from inside the base
electrode 13 flows into the electron acceleration layer 12 by
tunneling phenomenon. This electron is accelerated by the electric
field in the electron acceleration layer 12, and becomes a hot
electron. When this hot electron passes through the top electrode
11, a part of the electron loses energy by inelastic scattering and
the like. The electron having kinetic energy larger than a work
function .PHI. of the surface at a point of time when having
reached an interface between the top electrode 11 and a vacuum
(that is, the surface of the top electrode 11) is emitted from the
surface of the top electrode 11 into vacuum 10. In the present
specification, the current flowing between the base electrode 13
and the top electrode 11 by this hot electron is referred to as a
diode current Jd, and the current emitted into vacuum is referred
to as an emission current Je.
[0008] When compared with a field emission type cathode, the thin
film electron emitter has characteristics suitable for the display
apparatus such as strong resistance to surface contamination, small
in divergence of the emitted electron beam so that a
high-resolution display apparatus can be realized, small in
operation voltage, the drive circuit driver at low voltage, and the
like.
[0009] On the other hand, in the thin film electron emitter, only a
part of the current from among the drive currents is emitted into
vacuum (emission current Je). Here, the drive current is a current
flowing between the top electrode and the base electrode, and is
referred to also as the diode current Jd. A ratio .alpha. (electron
emission ratio .alpha.=Je/Jd) of the emission current Je to the
diode current Jd is approximately 0.1 to several tens %. That is,
to obtain the emission current Je, the drive current (diode
current) of Jd=Je/.alpha. is required to be fed to the thin film
electron emitter from the drive circuit. The electron emission
ratio .alpha. is referred to also as an electron emission
efficiency.
[0010] In this manner, in the matrix electron emitter display using
the thin film electron emitter as the electron emission element,
the current to drive the element is increased. Hence, it is
necessary that a current feeding capacity to the electron
emission-element's electrode (in this case, it denotes the base
electrode or the top electrode) from an electrode wiring is
sufficiently increased.
[0011] The electron emission element used for the matrix electron
emitter display includes a surface conduction electron emitter
element. The surface conduction electron emitter element, for
example, is described in Journal of the SID, vol. 5 (1997) pp.
345-348 (Non-Patent Document 4). The surface conduction electron
emitter element, as shown in FIG. 3, provides a gap of several
nanometers to several tens nanometers between a cathode electrode
film 813 and an anode electrode film 811. A voltage of several tens
volts is applied between the anode electrode film 811 and the
cathode electrode film 813. The electron emitted from the cathode
electrode film 813 flows into the anode electrode film 811, and
becomes the drive current Jd. A part of the electron constituting
the Jd does not flow into the anode electrode film 811, but becomes
an emitted electron 911, and reaches the acceleration electrode
122. The current of the emitted electron becomes an emitted current
Je (since the electron is a minus charge, the direction to which
the electron flows and the direction of the emission current are
reversed). The electron emission ratio Je/Jd is approximately
several % to ten %. In this manner, in the matrix electron emitter
display using the surface conduction electron emitter element as
the electron emission element, the current to drive the element is
increased. Hence, it is necessary that a current feeding capacity
to the electron emission-element's electrode (in this case, it
denotes the anode electrode film 811 and the cathode electrode film
813) from an electrode wiring is sufficiently high.
[0012] As described above, the acceleration electrode 122 provided
on the phosphor plate 602 is applied with a high voltage of
approximately 3 KV to 12 KV, and the electron emitted from the
electron emission element 301 is accelerated by this high voltage,
and after that, is bombarded onto the phosphor. The reason why the
electron is excited by high voltage of 3 KV or more is because, the
higher the acceleration voltage is, the deeper the penetration
depth of the electron to the phosphor is, and the luminous
efficiency and life of the phosphor are increased.
SUMMARY OF THE INVENTION
[0013] However, when the matrix electron emitter display is
operated for a long time in a state in which a high voltage is
applied to the acceleration electrode, a problem has arisen that a
long-term degradation of the electron emission element over
operation time is more serious. Here, the long-term degradation
over operation time of the electron emission element means
phenomenon such as long-term decrease in the amount of emission
current over operation time or damages of the electron emission
element. That is, such long-term degradation over operation time
becomes a factor of inhibiting the image quality and long life of
the image display apparatus.
[0014] An object of the present invention is to suppress the
long-term degradation over operation time or change with the
passage of time of the electron emission element in order to
provide an image display apparatus providing with high quality
images as well as a longer operation life.
[0015] From among various aspects of the invention disclosed in the
present specification, an outline of the representative aspect will
be described briefly as follows.
[0016] That is, the image display apparatus of the present
invention includes a display panel having a cathode plate and a
phosphor plate; and a drive circuit. The cathode plate includes a
plurality of electron emission elements, a plurality of scan lines
mutually in parallel, and a plurality of data lines mutually in
parallel and orthogonal to the scan lines. The electron emission
element is a thin film electron emitter, in which a top electrode,
an electron acceleration layer, and a base electrode are provided,
and a part of the top electrode constitutes an electron emission
region, and by applying a voltage between the top electrode and the
base electrode, electrons are emitted from the electron emission
region. The cathode plate includes a plurality of deflection
electrodes, and at the same time, has a center line at a position
dividing a distance between the inner edges of the adjacent
deflection electrodes in two equal parts, the electron emission
region is disposed so as not to include the center line.
[0017] Further, the image display apparatus of the present
invention includes a display panel having a cathode plate and a
phosphor plate, and a drive circuit. The cathode plate includes a
plurality of electron emission elements, a plurality of scan lines
mutually in parallel, and a plurality of data lines mutually in
parallel and orthogonal to the scan lines. The electron emission
element is a thin film electron emitter, in which a top electrode,
an electron acceleration layer, and a base electrode are provided,
and a part of the top electrode constitutes an electron emission
region, and by applying a voltage between the top electrode and the
base electrode, electrons are emitted from the electron emission
region. Between the electron emission region and the phosphor
plate, a shield electrode is provided, and in a projected plane
projecting a pattern of the electron emission region and a pattern
of the shield electrode, the electron emission region is disposed
so as to be included in the shield electrode.
[0018] Further, the image display apparatus of the present
invention is an image display apparatus including a display panel
having a cathode plate and a phosphor plate, and a drive circuit.
The cathode plate includes a plurality of electron emission
elements, a plurality of scan lines mutually in parallel, and a
plurality of data lines mutually in parallel orthogonal to the scan
lines. The electron emission element includes a first electrode and
a second electrode, and the first electrode is electrically
connected to the scan line, and the second electrode is
electrically connected to the data line, and the electron emission
element includes an electron emission region. When a voltage is
applied between the first electrode and the second electrode,
electrons are emitted from the electron emission region, and the
phosphor plate includes a phosphor and an acceleration electrode,
and by allowing the emitted electrons to excite the phosphor to
emit light, an image is displayed. In a projected plane projecting
a component on the phosphor plate and a component on the cathode
plate, the electron emission region is disposed so as not to be
superposed with a region formed with the phosphor.
[0019] Further, the image display apparatus of the present
invention includes a display panel having a cathode plate and a
phosphor plate, and a drive circuit. The cathode plate includes a
plurality of electron emission elements, a plurality of scan lines
mutually in parallel, and a plurality of data lines mutually in
parallel and orthogonal to the scan lines. The electron emission
element includes a first electrode and a second electrode, and the
first electrode is electrically connected to the scan line, and the
second electrode is electrically connected to the data line. The
electron emission element includes an electron emission region.
When a voltage is applied between the first electrode and the
second electrode, electrons are emitted from the electron emission
region. The phosphor plate includes a phosphor, a black matrix, and
an acceleration electrode, and by allowing the emitted electrons to
excite the phosphor to emit light, an image is displayed. In a
projected plane projecting a component on the phosphor plate and a
component on the cathode plate, the electron emission region is
disposed so as to be included in the black matrix.
[0020] According to the present invention, even when the electron
emission element is operated for a long time in a state in which a
high voltage of approximately 3 to 12V is applied to the
acceleration electrode, the degradation of the electron emission
element is reduced, and a high image quality is maintained, and an
operation life of the image display apparatus can be improved.
BACKGROUND OF THE INVENTION
[0021] FIG. 1 is a schematic view of a cross section of a matrix
electron emitter display;
[0022] FIG. 2 is a view for explaining an electron emission
mechanism of a thin film electron emitter;
[0023] FIG. 3 is a view showing a structure of a surface conduction
electron emitter element;
[0024] FIG. 4 is a schematic view showing potential distribution
inside a display panel;
[0025] FIG. 5 is a view showing degradation of an electron emission
element;
[0026] FIG. 6 is a cross section schematic view of the display
panel of a first embodiment of an image display apparatus according
to the present invention;
[0027] FIG. 7 is a view showing a projected plan view of a phosphor
region and an electron emission region according to the first
embodiment;
[0028] FIG. 8 is a view showing a cathode top plan view of the
first embodiment;
[0029] FIG. 9 is a view showing a drive waveform of the first
embodiment;
[0030] FIG. 10 is a view showing the cross section of the display
panel of the image display apparatus according to the present
invention;
[0031] FIG. 11 is a top plan view of a cathode plate of a second
embodiment of the image display apparatus according to the present
invention;
[0032] FIG. 12 is a view showing a mechanism by which an electron
beam is deflected;
[0033] FIG. 13 is a top plan view showing a part of the cathode
plate of the second embodiment of the image display apparatus
according to the present invention;
[0034] FIG. 14A is a cross section along line A-B of FIG. 13
showing a part of the cathode plate of the second embodiment of the
image display apparatus according to the present invention;
[0035] FIG. 14B is a cross section along C-D of FIG. 13 showing a
part of the cathode plate of the second embodiment of the image
display apparatus according to the present invention;
[0036] FIG. 15A is a top plan view for explaining a fabrication
process of the cathode plate of the second embodiment of the image
display apparatus according to the present invention;
[0037] FIG. 15B is a cross section along line A-B of FIG. 15A;
[0038] FIG. 15C is a cross section along line C-D of FIG. 15A;
[0039] FIG. 16A is a top plan view for explaining a fabrication
process of the cathode plate of the second embodiment of the image
display apparatus according to the present invention;
[0040] FIG. 16B is a cross section along line A-B of FIG. 16A;
[0041] FIG. 16C is a cross section along line C-D of FIG. 16A;
[0042] FIG. 17A is a top plan view for explaining a fabrication
process of the cathode plate of the second embodiment of the image
display apparatus according to the present invention;
[0043] FIG. 17B is a cross section along line A-B of FIG. 17A;
[0044] FIG. 17C is a cross section along line C-D of FIG. 17A;
[0045] FIG. 18A is a top plan view for explaining a fabrication
process of the cathode plate of the second embodiment of the image
display apparatus according to the present invention;
[0046] FIG. 18B is a cross section along line A-B of FIG. 18A;
[0047] FIG. 18C is a cross section along line C-D of FIG. 18A;
[0048] FIG. 19A is a top plan view for explaining a fabrication
process of the cathode plate of the second embodiment of the image
display apparatus according to the present invention;
[0049] FIG. 19B is a cross section along line A-B of FIG. 19A;
[0050] FIG. 19C is a cross section along line C-D of FIG. 19A;
[0051] FIG. 20A is a top plan view for explaining a fabrication
process of the cathode plate of the second embodiment of the image
display apparatus according to the present invention;
[0052] FIG. 20B is a cross section along line A-B of FIG. 20A;
[0053] FIG. 20C is a cross section along line C-D of FIG. 20A;
[0054] FIG. 21A is a top plan view for explaining a fabrication
process of the cathode plate of the second embodiment of the image
display apparatus according to the present invention;
[0055] FIG. 21B is a cross section along line A-B of FIG. 21A;
[0056] FIG. 21C is a cross section along line C-D of FIG. 21A;
[0057] FIG. 22A is a plan view for explaining a fabrication process
of the cathode plate of the second embodiment of the image display
apparatus according to the present invention;
[0058] FIG. 22B is a cross section along line A-B of FIG. 22A;
[0059] FIG. 22C is a cross section along line C-D of FIG. 22A;
[0060] FIG. 23A is a top plan view for explaining a fabrication
process of the cathode plate of the second embodiment of the image
display apparatus according to the present invention;
[0061] FIG. 23B is a cross section along line A-B of FIG. 23A;
[0062] FIG. 23C is a cross section along line C-D of FIG. 23A;
[0063] FIG. 24 is a view showing a connection of the display panel
and the drive circuit of the second embodiment of the image display
apparatus according to the present invention;
[0064] FIG. 25 is a view showing a drive waveform of the second
embodiment of the image display apparatus according to the present
invention;
[0065] FIG. 26 is a view showing a drive waveform of another
embodiment of the image display apparatus according to the present
invention;
[0066] FIG. 27 is a top plan view showing a part of the cathode
plate of a third embodiment of the image display apparatus
according to the present invention;
[0067] FIG. 28A is a cross section along A-B of FIG. 27 showing a
part of the cathode plate of a third embodiment of the image
display apparatus according to the present invention;
[0068] FIG. 28B is a cross section along C-D of FIG. 27 showing a
part of the cathode plate of a third embodiment of the image
display apparatus according to the present invention;
[0069] FIG. 29A is a view for explaining a current feeding ability
by a contact electrode shape, and corresponds to the embodiment of
FIG. 27;
[0070] FIG. 29B is a view for explaining a current feeding ability
by a contact electrode shape, and corresponds to the embodiment of
FIG. 13;
[0071] FIG. 30A is a view for explaining a definition of a height
in the present specification;
[0072] FIG. 30B is a view for explaining a definition of a height
in the present specification;
[0073] FIG. 31 is a view showing a part of the cathode plate of a
fourth embodiment of the image display apparatus according to the
present invention;
[0074] FIG. 32 is a cross section showing a part of the cathode
plate of a fifth embodiment of the image display apparatus
according to the present invention; and
[0075] FIG. 33 is a top plan view showing a part of the cathode
plate of a fifth embodiment of the image display apparatus
according to the present invention.
DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
[0076] Hereinafter, preferred embodiments of an image display
apparatus according to the present invention will be described in
detail with reference to several embodiments shown in the
drawings.
First Embodiment
[0077] A first embodiment of the present invention is an example in
a case when the present invention is applied to a MIM cathode, a
surface conduction electron emitter element and the like. Here,
first, a cause of degradation phenomenon of the electron emission
element generated when operated in a state in which a high voltage
is applied to a phosphor screen will be described.
[0078] As described in FIG. 1, the electron emitted from an
electron emission element 301 is accelerated by a phosphor-screen
voltage Va, and after that, is bombarded onto or irradiated at an
acceleration electrode 122 and a phosphor. Here, the
phosphor-screen voltage means a voltage applied to the acceleration
electrode 122, and it is typically Va=3 to 12 KV. When the electron
accelerated to 1 KV or more bombards the phosphor and gas
molecules, it is often that the electron ionizes atoms or
molecules, thereby to generate positive ion. The positive ion is
accelerated by the electric field between a phosphor plate 602 and
a cathode plate 601. The positive ion advances toward the cathode
plate, and bombards the cathode plate. When this positive ion
bombards the electron emission region of the electron emission
element, the electron emission element is degraded.
[0079] A specific description will be made by using FIG. 4. FIG. 4
is a view schematically showing a potential distribution between
the phosphor plate 602 and the cathode plate 601, a trajectory 921
of electron, and a trajectory 922 of the positive ion. Between the
phosphor plate 602 and the cathode plate 601, an approximately
uniform electric field is formed, and therefore, its potential
distribution is as shown in the right side graph of FIG. 4. Now, it
is assumed that a positive ion is generated in the distance Z=z0
from the cathode plate. Assuming that the potential of z=z0 is
V(z0), when this positive ion bombards or irradiates the electron
emission element 301 by tracing the trajectory 922, kinetic energy
carried by the positive ion is V(z0). Consequently, from among the
space between the phosphor plate 602 and the cathode plate 601, the
ion generated at a place close to the phosphor plate 602 enters the
electron emission element 301 with higher energy.
[0080] FIG. 5 shows a long-term change over operation time of diode
current when the image display apparatus using the MIM cathode for
the electron emission element 301 is operated for a long time. The
axis of ordinate plots a value having normalized the diode current
by an initial value (that is, a value divided by the initial diode
current). When the phosphor screen voltage Va is 200V, the diode
current is almost constant even when the apparatus is operated for
a long time. However, when apparatus is operated with the phosphor
screen voltage Va set to 3 KV, an amount of long-term change over
operation time or change with the passage of time of the diode
current is increased.
[0081] To check a cause of this degradation, a display panel
deposited with ITO (Indium Tin Oxide) only as a phosphor screen,
that is, a display panel not including a phosphor on the phosphor
screen was prepared, and its long-term change of the diode current
over operation time was checked (characteristics described as "3
KV, ITO" in FIG. 5). As a result, when a panel not including the
phosphor (described as "3 KV, ITO" in FIG. 5) and an ordinary panel
including the phosphor (described as [3 KV, phosphor] in FIG. 5)
are compared, the panel including the phosphor is further larger in
the amount of long-term change of the diode current over operation
time. From this result, the following became clear.
[0082] There are mainly two kinds of causes which generate the
positive ion. A first cause is a phosphor 114, and a second cause
is a small amount of residual gas molecules inside the display
panel. Since the phosphor 114 is bombarded or irradiated by the
electron having an energy Va, heat is generated, so that the
molecules are desorbed or the molecules can be desorbed or the
phosphor surface can be decomposed owing to the electron
bombardment. When the electron is bombarded onto or irradiated at
the molecules and atoms generated at this time, ions are generated.
Further, the potential of the phosphor screen, as shown in FIG. 4,
is the maximum between the phosphor plate 602 and the cathode plate
601, and therefore, the positive ion generated in the phosphor is
great in incident energy at the time of irradiation to the electron
emission element 301, and the damages given to the electron
emission element is great.
[0083] Hence, in the first embodiment of the present invention, to
prevent the positive ion generated by the phosphor 114 from
bombarding or irradiating the electron emission element, the
phosphor 114 and the electron emission region are appropriately
disposed as described below.
[0084] FIG. 6 is a view schematically showing a cross section of
the display panel according to the first embodiment of the present
invention. While the display panel is typically composed of sub
pixels of 1000 rows X several thousand columns, FIG. 6 shows only
three sub pixels from among those sub pixels. Here, the sub pixel
corresponds to each sub pixel of a red color sub pixel, a blue
color sub pixel, and a green color sub pixel constituting one color
pixel in a color image display apparatus. In a monochrome image
display apparatus, the sub pixel corresponds to one pixel. The
cathode plate 601 is formed with an electron emission element
having an electron emission region 35. In FIG. 6, only the electron
emission region 35 is shown from among the electron emission
elements.
[0085] In the present specification, the electron emission region
35 denotes a part from which the electron is emitted from among the
constituent components of the electron emission elements. In the
thin film electron emitter, the electron emission region 35
corresponds to a top electrode on an electron acceleration layer.
In a field emission electron emitter, the electron emission region
35 corresponds to an electron emitter tip. In the case of the
surface conduction electron emitter element shown in FIG. 3, the
electron emission region 35 corresponds to a cathode electrode film
813 and an anode electrode film 811.
[0086] In the case of a structure in which a plurality of electron
emission sites are provided inside one sub pixel, the entire region
provided with the electron emission sites inside one sub pixel is
defined as the electron emission region 35. For example, in the
case of the HEED cathode described in the Non-Patent Document 5, a
plurality of electron emission sites having a diameter of
approximately 1 .mu.m are included in the top electrode inside one
sub pixel, but in this case, the entire electron emission site
inside one sub pixel is defined as the electron emission region
35.
[0087] The cathode plate 601 is formed with a beam deflection
electrode A 331 and a beam deflection electrode B 332. By applying
a voltage difference between the beam deflection electrode A and
the beam deflection electrode B so as to generate a lateral
electric field in a space close to the electron emission region 35,
the trajectory 921 of the electron emitted from the electron
emission region 35 is bent (deflected).
[0088] The phosphor screen 602 is formed with a phosphor region 114
and a black matrix 120. The phosphor region 114 is patterned with
three kinds of a red color phosphor, a green color phosphor and a
blue color phosphor in the color image display apparatus. Further,
the acceleration layer 122 is formed. The fabrication method of the
phosphor plate will be described in detail later according to a
second embodiment. Corresponding to the deflected trajectory 921 of
the electron beam, the position of the phosphor region 114 is
disposed to be shifted from the position of the electron emission
region 35.
[0089] The characteristic of the present invention is a positional
relation between the phosphor region 114 and the electron emission
region 35. FIG. 7 is a top plan view (projected plan view) showing
the phosphor region 114 and the electron emission region 35 by
projecting them in the same plane (a projected plane). As apparent
from FIG. 7, in the projected plan view, the phosphor region 114
and the electron emission region 35 of the electron emission
element are disposed not to be superposed with each other. In the
phosphor screen, since the regions other than the phosphor region
114 are formed with the black matrix 120, from another point of
view, the electron emission region 35 is included in the black
matrix 120 in the projected plan view.
[0090] As shown in FIG. 6, the positive ion generated in the
phosphor region 114 is accelerated along the trajectory 922 of the
positive ion, and bombards the cathode plate 601. Since a mass of
the positive ion is more than 1000 times larger than that of the
electron, the positive ion approximately goes straight almost not
bending the trajectory in a lateral electric field, and therefore,
the positive ion bombards the cathode plate directly below the
phosphor region 114. Consequently, when the phosphor region 114 and
the electron emission region 35 are disposed as shown in FIGS. 6
and 7, the positive ion is not irradiated at the electron emission
region 35, and no degradation of the electron emission element
occurs.
[0091] In FIGS. 6 and 7, as a means for deflecting the electron
beam trajectory 921, though the lateral electric field by the
potential difference between an electron beam deflection electrode
A 331 and a beam deflection electrode B 332 is used, this is just
an example, and even when another method of deflecting the
trajectory is used, the same effect can be obtained. For example,
as described in the embodiment to be described later, by
constituting an electron lens by forming an appropriate electrode
shape on the cathode plate 601, the beam may be deflected. Further,
the electron emission element 301 used in the present embodiment
may use any of the thin film electron emission element including
the MIM cathode, the surface conduction electron emitter element,
and the electric field emission type electron emission element
including a carbon nanotube cathode.
[0092] FIG. 8 is a top plan view showing an electrode structure of
the cathode plate 601 used in the first embodiment of the present
invention. In FIG. 8, a part corresponding to the sub pixels of 3
rows.times.3 columns in the display panel was shown. Further, in
FIG. 8, from among the components constituting the cathode plate,
the electron emission region 35, the beam deflection electrode A
331 and the beam deflection electrode B 332, and a scan electrode
310 only are described.
[0093] Each scan electrode 310 has one side (upper side in FIG. 8)
connected with the beam deflection electrode A 331, and has the
opposite side connected with the beam deflection electrode B 332.
Further, in FIG. 8, one electrode of an electron emission element
301-n (not shown) corresponding to an electron emission region 35-n
is electrically connected to a scan line electrode 310-n. Here, n=1
to 3. Here, the "one electrode" of the electron emission element
301 is specifically as follows. In the case of the thin film
electron emitter, it denotes a top electrode 11. In the case of the
surface conduction electron emitter of FIG. 3, it is the anode
electrode film 811. In the case of the field emission type electron
emitter, it is a gate electrode.
[0094] Although not shown in FIG. 8, a data electrode 311 is
disposed in a direction orthogonal to the scan electrode 310. The
data electrode 311 is electrically connected to the other electrode
of the electron emission element 301. Here, "the other electrode"
of the electron emission element 301 is specifically as follows. In
the case of the thin film electron emitter, it is the base
electrode 13. In the case of the surface conduction electron
emitter of FIG. 3, it is a cathode electrode film 813. In the case
of the field emission type electron emitter, it is an emitter
electrode. The scan electrode 310-(n-1) and the electron emission
element 301-n corresponding to the electron emission region 35-n
are not electrically connected.
[0095] FIG. 9 is a view showing waveforms of applied voltage to the
scan electrode 310-n. Each scan electrode is sequentially applied
with a scan pulse 750. The scan pulse 750 has a positive voltage
amplitude V.sub.R1. During a period when the scan pulse 750 is
applied, the electron emission element 301 applied with a data
pulse 751 in a data electrode emits the electron from the electron
emission region 35.
[0096] As an example, a period of the time t2 to the time t3 is
considered. In this period, since the scan pulse 750 is applied to
the scan electrode 310-2, the electron is emitted from an electron
emission region 35-2. At this time, the beam deflection electrode A
331 connected to the scan electrode 310-2 is applied with the
positive voltage V.sub.R1, and the voltage of the beam deflection
electrode B 332 connected to a scan electrode 310-1 is zero.
Consequently, as described in FIG. 6, close to the electron
emission region 35-2, a lateral electric field is formed. By this
electric field, as shown in FIG. 6, the electron beam trajectory
921 is deflected.
[0097] In the present embodiment, a case of using a positive
polarity pulse as the scan pulse 750 has been shown as an example.
It is obvious that the similar arrangement can be realized even
when a negative polarity pulse is used as the scan pulse. In this
case, the scan electrode may be connected with a terminal of the
negative polarity side of the electron emission element, and the
data electrode may be connected with a terminal of the positive
polarity side of the electron emission element.
Second Embodiment
[0098] A second embodiment of the present invention uses a thin
film electron emitter as an electron emission element. As compared
with another cathode such as a field emission type cathode, the
thin film electron emitter is small in spatial divergence of
emitted electron beam. The reason is as follows. In the thin film
electron emitter, the electron accelerated in an electron
acceleration layer is emitted into vacuum from a top electrode. In
the thin film electron emitter, since the top electrode and a base
electrode are mutually disposed in opposition in parallel, the
electric field inside the electron acceleration layer is a uniform
electric field. Since the electron is accelerated by this uniform
electric field, the spatial divergence of the emitted electron
becomes small. That the spatial divergence of the emitted electron
beam is small is favorable characteristics because a
high-resolution image display apparatus can be realized.
[0099] On the other hand, as evident from FIG. 4, when the spatial
divergence of the beam is small, a greater part of the positive ion
generated somewhere along an electron trajectory 921 is bombarded
onto or irradiated at an electron emission region 35. Hence, the
thin film electron emitter which is excellent in beam
directionality is greatly affected by the degradation of the
electron emitter by a positive ion, and its countermeasure is
required. In the present embodiment, an image display apparatus
enhanced in durability against ion bombardment at the thin film
electron emitter is provided.
[0100] FIG. 10 schematically shows a cross section of a display
panel according to the second embodiment of the present invention.
In FIG. 10, to make the characteristics of the second embodiment
clear, main constituent components only are taken out and
described. With respect to the thin film electron emitter, the
electron emission region 35 only is described. The detail structure
will be described later together with the manufacturing method
thereof. Further, a top plan view corresponding to FIG. 10 is shown
in FIG. 11. The cross section taken along line A-B of FIG. 11
corresponds to FIG. 10.
[0101] A scan line 310 is electrically connected to the electrode
of an electron emission element 301 through a contact electrode 55.
The electron emission element 301 has the electron emission region
35. In FIG. 11, a scan line 310-2 is connected to the electron
emission element having an electron emission region 35-2. Further,
a cathode plate 601 is provided with a deflection electrode 315.
The deflection electrode 315 is at a position higher than the
electron emission region 35, that is, formed thick in film
thickness, and a local projection or locally projected high region
is formed on the cathode plate 601.
[0102] The dotted lines G-H 430 shown in FIGS. 10 and 11 show a
position of the center point of the distance (that is, the inside
distance) between inner edges of the adjacent defection electrodes
315. That is, d1=d2 in FIG. 11. In the present specification, the
G-H line 430 thus defined is referred to as a center line 430. The
characteristics of the present embodiment are that the electron
emission region 35 is disposed at such a position where the
electron emission region 35 does not include the center line G-H
430 between the deflection electrodes forming the local projection.
By taking such a disposition, the emitted electron beam can be
deflected as described later.
[0103] A beam deflection mechanism in the present embodiment will
be described with reference to FIG. 12. In FIG. 12, there is shown
schematically by dotted lines an equipotential surface 441 formed
by periodic structure of the deflection electrode. An electron lens
formed by this equipotential surface 441 deflects the electron beam
emitted from the electron emission region 35 towards the center
line 430. For purpose of illustration, in FIG. 12, a virtual
electron emission region 435 was virtually disposed, and a
trajectory 921-2 of the electron beam emitted from the virtual
electron emission region 435 was also shown. The beam trajectory
921-2 is also deflected towards the center line 430.
[0104] From this, it is evident that, if the electron emission
region 35 is disposed not to straddle the center line 430, the
emitted electron is deflected like the trajectory 921. This is a
deflection principle of the electron beam in the present
invention.
[0105] As described in FIG. 12, the electrode shape is preferably
designed such that the emitted beam trajectory 921 from the
electron emission region and the emitted beam trajectory 921-2 from
the virtual electron emission region 435 have a cross-over
(intersection). By so doing, in the actual structure taking off the
virtual electron emission region 435, the beam deflection amount
becomes large, and the positive ion is further prevented from
entering the electron emission region.
[0106] The main factors that decide the characteristics of the
electron lens for playing a role of deflecting the electron beam
trajectory are four of (a) a difference in height between the
deflection electrode and the top electrode, (b) a voltage
difference between the deflection electrode and the top electrode,
(c) a period of the deflection electrode (distance between the
adjacent deflection electrodes), and (d) a phosphor screen voltage
Va. The factor (a) (a difference in height between the deflection
electrode and the top electrode) is, as evident from FIG. 12, an
important factor to decide the electron lens characteristics. The
larger the difference in height is, the larger the amount of beam
deflection is.
[0107] Here, the "height" of the electrode is a height measured
from the surface of a substrate 14 constituting the cathode plate
601, and is defined as a length from the surface of the substrate
14 to the highest region (highest part) of the electrode. That is,
similarly to FIG. 30A to be described later, when the deflection
electrode 315 is directly formed in the substrate 14, its film
thickness becomes a height h0. Further, similarly to FIG. 30B, when
the deflection electrode 315 is formed on a dielectric layer 385, a
length up to the highest position of the deflection electrode 315
(h0 in the figure) defines the height. The "height" of the top
electrode is also similarly defined. Even in the case of FIG. 30B,
the height h0 mainly controls the electron lens
characteristics.
[0108] As evident from the description in FIG. 12, in the present
embodiment, at both sides of the electron emission region, the
deflection electrode is present at a position higher than the
electron emission region, so that the lateral electric field is
formed, and the trajectory of the electron beam emitted from the
electron emission region is deflected. To obtain a sufficient beam
deflection amount, the deflection electrode is preferably made
higher than the height of the top electrode by 2 .mu.m or more.
[0109] As evident from the description in FIG. 12, the period of
the deflection electrode (distance between the adjacent deflection
electrodes) also affects the electron lens characteristics. When
this period is made consistent with the period of the sub pixel,
the beam deflection amount of each sub pixel becomes constant,
which is preferable.
[0110] Further, as evident from the description in FIG. 12, the
electrode (referred to as "protruded electrode") at a position
higher than the height of the top electrode may be periodically
disposed close to the top electrode. Consequently, even when the
electrode is an electrode having a role different from the
deflection electrode, if this electrode (protruded electrode) has a
sufficient height difference with the top electrode, and moreover,
is periodically disposed, such electrode can be taken as the
deflection electrode. In the present embodiment, in such a case,
the protruded electrode is regarded as performing the function of
the deflection electrode, and such protruded electrode is taken as
the deflection electrode.
[0111] Next, the image display apparatus of the present embodiment
will be described more in detail. First, a fabricating method of a
display panel 100 constituting the image display apparatus will be
described. The display panel 100 is formed of the cathode plate 601
and the phosphor plate 602. FIG. 13 is a top plan view showing a
part of the cathode plate 601. In FIG. 13, the sub pixels of 2
rows.times.2 columns were taken out and illustrated. FIGS. 14A and
14B are cross sections showing a part of the cathode plate 601. A
cross section along A-B of FIG. 13 corresponds to FIG. 14A, and a
cross section along C-D corresponds to FIG. 14B. FIG. 13 is a top
plan view taking off the top electrode 11. In reality, as evident
from the cross sections of FIG. 14, the top electrode 11 is
deposited as a film on the entire surface.
[0112] FIG. 13 describes in detail a specific constitution example
in a case when the thin film electron emitter is used as the
electron emission element 301 in FIG. 11. Consequently, in FIG. 13,
the relation of connection between the electron emission element
301 and the electrode wiring is the same as that in FIG. 11.
Hereinafter, the electron emission region 35 corresponding to an
electron emission element 301-n will be referred to as an electron
emission region 35-n. Now, to describe by using reference numerals
of FIG. 11, feeding is made to an electron emission element 301-2
from a scan line 310-2 via the contact electrode 55, and from the
adjacent scan line 310-1 (corresponding to a busline electrode 32
in FIG. 13), the deflection electrode 315 is disposed along a
longer side of the electron emission region 35-2. In the present
embodiment, by electrically connecting the deflection electrode 315
to the scan line 310, an advantage is afforded that the wiring is
simplified.
[0113] The constitution of the cathode plate 601 is as follows. In
FIGS. 14A and 14B, on an insulating substrate 14 such as glass, a
thin film electron emitter 301 (electron emission element 301 in
the present embodiment) composed of a base electrode 13, an
insulating layer 12, and a top electrode 11 is formed. The busline
electrode 32 is electrically connected to the top electrode 11 via
a contact electrode 55. The busline electrode 32 functions as a
feeding line to the top electrode 11. That is, it plays a role of
carrying the current to a position of this sub pixel from a drive
circuit. Further, in the present embodiment, the busline electrode
32 functions as the scan electrode 310.
[0114] In the present embodiment, as the electron emission element
301, a thin film electron emitter is used. As shown in FIG. 14,
three of the base electrode 13, a tunneling insulator 12, and the
top electrode 11 are the basic constituents of the thin film
electron emitter. The electron emission region 35 of FIG. 13 is a
place corresponding to the tunneling insulator 12. From the surface
of the top electrode 11 over the electron emission region 35, the
electron is emitted into vacuum.
[0115] In the present embodiment, the region (region contacting the
tunneling insulating layer 12) of a part of the data line 311
serves as the base electrode 13. In the present specification, from
among the data lines 311, a part contacting the tunneling insulator
12 is referred to as the base electrode 13. In FIG. 13, a threefold
rectangular is disposed at a part corresponding to each sub pixel.
The rectangular region of the innermost side denotes the electron
emission region 35, and this is equivalent to the innermost
circumference of a tapered part (slope region) of a first
interlayer insulating film 15. The rectangular of its outside is
equivalent to the outermost circumference of a tapered film of the
first interlayer insulating film 15. Its outside (outermost
circumference) is an opening of a second interlayer insulating
layer 51.
[0116] In the present embodiment, the scan electrode 310 is formed
of the bus electrode 32. Further, in the present embodiment, a
spacer 60 is provided on the scan electrode 310. The spacer 60 is
not required to be provided on all scan electrodes, but may be
provided every several scan electrodes. The spacer 60 is
electrically connected to the scan electrode 310, and functions to
flow the current flowing from the acceleration electrode 122 of the
phosphor plate 602 through the spacer 60, and functions to flow
electrical charges charged on the spacer 60. In FIGS. 14A and 14B,
a contraction scale in height direction is optional. That is, while
the base electrode 13, the top electrode, and the like are several
.mu.m or less in thickness, a distance between the substrate 14 and
a face plate 110 is a length of approximately 1 to 3 mm.
[0117] In FIG. 13, a line G-H existing at a position that divides
the distance between the inner edges of adjacent deflection
electrodes 315 into two equal parts is referred to as a center line
430. That is, in FIG. 13, d1=d2. The electron emission region 35 is
disposed so as not to stride the center line 430, and this is the
characteristic of the present embodiment.
[0118] The fabrication method of the cathode plate 601 will be
described with reference to FIGS. 15 to 23. FIGS. 15 to 23 show a
process of fabricating the thin film electron emitter on the
substrate 14. In these figures, the thin film electron emitters
corresponding to the sub pixels of two rows.times.two columns are
shown. A case A (FIGS. 15A-23A) of each figure indicates a top plan
view, the cross section along line A-B is shown in a case B (FIGS.
15B-23B), and the cross section along line C-D is shown in a case C
(FIGS. 15C-23C).
[0119] On the insulating substrate 14 such as glass, an Al alloy is
formed, for example, in film thickness of 300 nm as a material of
the base electrode 13 (data line 311). Here, Aluminum-Neodymium
(Al--Nd) alloy was used. The formation of this Al alloy film
employs, for example, a sputtering method or resistive heating
evaporation, and the like. Next, this Al alloy film is subjected to
resist formation by photolithography and subsequent etching so as
to be fabricated in stripe-shaped, thereby forming the base
electrode 13. The resist materials employed here may be suitable
for etching, and further, etching adapted can be both wet etching
and dry etching.
[0120] Next, the resist is coated, and is exposed by ultraviolet
ray to be patterned, so that a resist pattern 501 of FIG. 15 is
formed. For the resist, for example, a quinonediazide based
positive resist is used. Next, with the resist pattern 501 attached
as it is, anodization is performed, thereby to form a first
interlayer insulating film 15. In the present embodiment, this
anodization is performed to the extent of anodization voltage of
100V, and the film thickness of the first interlayer insulating
film 15 was made to the extent of 140 nm. After that, the resist
pattern 501 is removed. This is a state shown in FIGS. 16A-16C.
[0121] Next, the surface of the base electrode 13 covered with the
resist 501 is anodized so as to form an insulator 12. In the
present embodiment, anodization voltage was set to 4V, and the
insulator film thickness was made 9.7 nm. This is a state shown in
FIGS. 17A-17C. The region in which the insulator 12 is formed
becomes the electron emission region 35. That is, the region
surrounded by the first interlayer insulating film 15 is the
electron emission region 35.
[0122] When a film thickness d of an anodization insulating film
obtained by anodizing aluminum is thinner in thickness than
approximately 20 nm, it is disclosed that a relationship of
d(nm)=1.36.times.(VAO+1.8) is established (Non-Patent Document 3).
When the insulator film thickness in a case when an anodization
voltage is 4V is determined from this relational formula, it
becomes 7.9 nm. However, as a result of measuring by the film
thickness by transmission type electron microscope, it was found
that the film thickness generated by anodization voltage 4V is 9.7
nm. The above described film thickness value adopts this actual
measurement.
[0123] Next, by the following procedure, a second interlayer
insulating film 51 and an electron emission region protection layer
52 are formed (FIGS. 18A-18C). A pattern of the second interlayer
insulating film 51 is formed at an intersection region with the
busline electrode 32 and the data electrode 311, and the second
interlayer insulating film 51 has a pattern in which the electron
emission region 35 is exposed. However, at the processing stage of
FIGS. 18A-18C, the electron emission region 35 is covered with the
electron emission region protection layer 52. The second interlayer
insulating layer 51 and the electron emission region protection
layer 52, after having deposited silicon nitride (SiNx), Silicon
Oxide (SiOx), and the like, are patterned by etching. In the
present embodiment, silicon nitride film of 100 nm in thickness was
employed. Etching is performed by dry etching using an echant
consisting essentially of, for example, CF.sub.4 and SF.sub.6.
[0124] The second interlayer insulating film 51 is formed to
improve insulation property between the scan electrode and the data
electrode. The electron emission region protection layer 52
protects a part (that is, insulator 12) serving as the electron
emission region 35 from the process damages at the subsequent
processes; and as described later, the electron emission region
protection layer 52 is removed at a later process. In the present
embodiment, the second interlayer insulating film 51 and the
electron emission region protection layer 52 are formed by the same
material and the same process.
[0125] Next, the materials constituting a contact electrode 55, a
busline electrode 32, and a busline upper layer 34 are deposited in
this order (FIGS. 19A-19C). In the present embodiment, the contact
electrode 55 used chrome (Cr) of 100 nm in thickness, the busline
electrode 32 used aluminum (Al) of 10 .mu.m in thickness, and the
busline electrode upper layer 34 used chrome (Cr) of 200 nm in
thickness. These electrodes were deposited by sputtering. The
material of the busline electrode 32, when a material having high
conductivity is used, becomes low in wiring resistance, and can
reduce a voltage drop at the electrode, and therefore, it is
preferable.
[0126] Next, the busline electrode upper layer 34 and the busline
electrode 32 are patterned by etching, thereby to form the busline
electrode 32 (FIGS. 20A-20C), into a pattern in which the contact
electrode 55 is exposed so as to enable the top electrode 11 to
connect with the contact electrode 55 in a later step. In this
process, a deflection electrode 315 is formed simultaneously. As
shown in FIGS. 20A and 20C, by using a pattern provided with a
protrusion on the busline electrode 32, the protrusion is used as
the deflection electrode 315. That is, the busline electrode 32 and
the deflection electrode 315 are made of the same material. By so
doing, an advantage is afforded that they can be manufactured by
the same manufacturing process as the conventional art.
[0127] Next, the contact electrode 55 is patterned by etching
(FIGS. 21A-21C). Here, the pattern of the contact electrode 55
determines a current feeding state from the contact electrode 55 to
the electron emission region 35. As shown in FIG. 21A, the contact
electrode 55 is patterned such that, from among four sides of the
electron emission region 35, two sides including a longer side are
abutted on the contact electrode 55. As described above, the
contact electrode region 55 is designed to have a cathode structure
in which the current is fed through two sides including a longer
side of the electron emission region 35, so that a current feeding
ability is improved.
[0128] As shown by the arrow mark in the cross section of FIG. 21B,
one side (region shown by the arrow mark in the figure) of the
contact electrode 55 forms an undercut for the busline electrode
32, and forms an overhang for electrically separating the top
electrode 13 in the subsequent process. By presence of this
undercut, the top electrodes of the sub pixels connected to the
adjacent scan line are mutually electrically insulated (separated).
This is referred to as "pixel separation". Since the busline
electrode 32 and the deflection electrode 315 are made from the
same process, even below the scan electrode 315, the undercut is
formed, which is electrically insulated with the adjacent scan
line.
[0129] An undercut amount of the contact electrode 55 is controlled
in the following manner. A part in which the undercut is formed
etches the contact electrode 55 by using a side of the busline
electrode 32 as a photomask. Consequently, the contact electrode 55
generates the undercut for the busline electrode 32. On the other
hand, when the undercut amount is too large, the busline electrode
32 collapses, and this brings the busline electrode 32 into contact
with the second interlayer insulating film 51, thereby to eliminate
the overhang. Hence, to prevent the formation of an excessively
large undercut, a material nobler in standard electrode potential
than the material of the busline electrode 32 is used as the
material of the contact electrode 55. That is, as the contact
electrode 55, the material higher in standard electrode potential
than the material of the busline electrode 32 is used.
[0130] When the busline electrode is made of aluminum, such a
material includes, for example, chrome (Cr), molybdenum (Mo), Cr
alloy or the like, and an alloy including these metals as
components, for example, Molybdenum-Chrome-Nickel (Mo--Cr--Ni)
alloy. By so doing, by local cell mechanism, side etching of the
contact electrode 55 is stopped halfway, so that the undercut
amount can be prevented from increasing excessively. Further, by
controlling the area of the busline electrode to be exposed to the
etching liquid, the local cell mechanism can be controlled because
the busline electrode material is less nobler material in standard
electrode potential. In this way, the stopping position (that is,
the undercut amount) of the side etching of the contact electrode
55 can be controlled. For this purpose, the busline electrode upper
layer 34 with chrome (Cr) taken as material is formed.
[0131] As evident from the above description, the material of the
contact electrode 55 preferably uses a nobler (higher) material in
standard electrode potential than the material of the busline
electrode 32.
[0132] Next, the electron emission region protection layer 52 is
removed by dry etching and the like (FIGS. 22A-22C). Next, the top
electrode 11 is formed, thereby completing the cathode plate 601
(FIGS. 23A-23C). In the present embodiment, as the top electrode
11, a stacked film of iridium (Ir), platinum (Pt), gold (Au) was
used. The top electrode 11 was formed by sputtering deposition.
Although the entire surface is actually deposited with the top
electrode 11, for the purpose of explaining the structure simply,
FIG. 23A shows a view in which the top electrode is removed.
Further, the position of the data line 311 is shown by dotted
line.
[0133] As shown in FIGS. 23A-23C, the electric current is supplied
from the busline electrode 32 severing as a feeding line to the top
electrode 11 of the electron emission region 35 via the contact
electrode 55. On the other hand, as described above, since the
contact electrode 55 is formed with an appropriate amount of the
undercut, they are mutually insulated electrically between the scan
electrodes 310.
[0134] In the present embodiment, a cathode structure in which two
features are taken in, is adopted; a feature (feature "A") that two
sides including a longer side of the electron emission region are
used as a feed path to the top electrode 11 in the electron
emission region 35 from the busline electrode 32, and a feature
(feature "B") that a step in the second interlayer insulating film
is removed from the feed path to the top electrode in the electron
emission region.
[0135] The constitution of a phosphor 602 is as follows. As shown
in FIG. 14, a transparent faceplate 110 such as glass is formed
with a black matrix 120, and further, on a position facing each
electron emission region, the phosphor 114 is formed. In the case
of the color image display apparatus, as the phosphor 114, a red
phosphor, a green phosphor, and a blue phosphor are patterned.
Further, the acceleration electrode 122 is formed. The acceleration
electrode 122 is formed of an aluminum film of approximately 70 nm
to 100 nm in thickness. The electron emitted from the thin film
electron emitter 301 is accelerated by acceleration voltage applied
to the acceleration electrode 122, and after that, when the
electron enters the acceleration electrode 122, it pass through the
acceleration electrode and bombards the phosphor 114, thereby to
excite the phosphor to emit light. The detail of the fabrication
method of the phosphor plate 602 is disclosed, for example, in
Japanese Patent Application Laid-Open Publication No.
2001-83907.
[0136] As shown in FIG. 10, in the present embodiment, since the
trajectory of the emitted electron is deflected, a position of the
phosphor region 114 is not placed directly above the electron
emission region 35, but is disposed in consideration of a deflected
amount of the beam. That is, the center position of the electron
emission region 35 and the center position of the phosphor region
114 are shifted to each other. Between the cathode plate 601 and
the phosphor plate 602, a suitable number of spacers 60 are
disposed. As shown in FIG. 1, the cathode plate 601 and the
phosphor plate 602 are sealed by interposing or holding a frame
component 603. Further, the space surrounded by the cathode plate
601, the phosphor plate 602, and the frame component 603 are pumped
to vacuum. By the above described procedure, the display panel is
completed.
[0137] FIG. 24 is a connection diagram toward the drive circuit of
the display panel 100 fabricated in this manner. The scan electrode
310 is connected to a scan electrode drive circuit 41, and the data
electrode 311 is connected a data electrode drive circuit 42. The
acceleration electrode 122 is connected to an acceleration
electrode drive circuit 43 through a resistor 130. A dot at the
intersection of an n-th scan electrode 310Rn and an m-th data
electrode 311Cm is represented by (n, m).
[0138] A resistance value of the resistor 130 was set as follows.
For example, in the display apparatus having a diagonal size of 51
cm (nominal 20 inches), a display area is 1240 cm.sup.2. When the
distance between the acceleration electrode 122 and the cathode is
set to 2 mm, a capacitance Cg between the acceleration electrode
122 and the cathode is about 550 pF. To make a time constant
sufficiently longer than occurrence time (approximately 20 nano
seconds) of vacuum discharge, for example, 500 nano seconds, it is
sufficient to set a resistance value Rs of the resistor 130 at
900.OMEGA. or more. In the present embodiment, the value was set to
18 K.OMEGA. (time constant 10 .mu.s). In this manner, by inserting
a resistor having the resistance value to satisfy the time constant
Rs.times.Cg>20 ns between the acceleration electrode 122 and the
acceleration electrode drive circuit 43, an effect of suppressing
an occurrence of the vacuum discharge inside the display panel can
be obtained.
[0139] FIG. 25 shows a waveform of the generated voltage of each
drive circuit. Although not illustrated in FIG. 25, the
acceleration electrode 122 is applied with the voltage (phosphor
screen voltage Va) of approximately 3 to 10 KV. At the time t0,
since voltage of any of the electrodes is zero, no electron is
emitted, and consequently, the phosphor 114 does not emit
light.
[0140] At the time t1, a scan pulse 750 of the voltage which is
V.sub.R1=Vs is applied to the scan electrode 310R1, and the scan
electrode is thereby put into a selection state. The non-selected
scan electrodes, that are the scan electrodes other than the
selected scan electrode 310R1, are supplied with a voltage which is
Vns. In the present embodiment, Vns=0V. Further, at the time t1, a
data pulse 751 of a voltage which is -V.sub.C1, is applied to data
electrodes 311C1 and 311C2. Between the base electrode 13 and the
top electrode of dots (1, 1) and (1, 2), a voltage which is
(V.sub.C1+V.sub.R1) is applied, and therefore, if
(V.sub.C1+V.sub.R1) is set to equal to or higher than the voltage
of starting an electron emission (a threshold voltage of electron
emission), the electron is emitted into vacuum 10 from the thin
film electron emitter of these two dots.
[0141] In the present embodiment, V.sub.R1=VS=+4V and
-V.sub.C1=-3V. The emitted electron is accelerated by the voltage
applied to the acceleration electrode 122, and after that, bombards
the phosphor 114, thereby to excite the phosphor 114 to emit light.
At the time t2, when a voltage which is V.sub.R1=VS is applied to a
scan electrode 310R2, and a voltage which is -V.sub.C1, is applied
to a data electrode 311C1, similarly the dots (2, 1) are lighted.
In this manner, when the voltage waveform of FIG. 25 is applied,
only the dots marked with shaded lines in FIG. 24 are lighted.
[0142] In this manner, it is possible to display a desired image or
information by changing the signal applied to the data electrode
311. Further, by suitably changing magnitude of the voltage
-V.sub.C1 applied to the data electrode 311 according to the image
signal, an image with gradation can be displayed.
[0143] As shown in FIG. 25, at the time t4, a voltage which is
-V.sub.R2 is applied to all the scan lines 310. In the present
embodiment, -V.sub.R2=-3V. At this time, since the applied voltage
to all the data electrodes 311 is 0V, a voltage of -V.sub.R2=-3V is
applied to the thin film electron emitter 301. In this way, a
voltage whose polarity is reverse to the voltage applied during
electron emission is applied; the reverse polarity pulse is called
reverse pulse 754. By applying a reverse polarity voltage,
electrical charges accumulated in traps in the insulating layer 12
are liberated, and it is possible to improve a lifetime
characteristic of a thin-film electron emitter. Further, if the
vertical blanking period of a video signal is used as a period of
applying the reverse pulse (t4 to t5 and t8 to t9 of FIG. 25),
consistency with the video signal is good. In the description of
FIGS. 24 and 25, for the sake of simplicity, a description has been
made by using an example of 3.times.3 dots. However, in the actual
image display apparatus, the number of scan electrodes is several
hundreds to several thousands, and the number of data electrodes is
also several hundreds to several thousands.
[0144] FIG. 26 shows another driving method. In this driving
method, in the period of the time t2 to t3, the scan pulse 750 is
applied the scan electrode 310R2, and a deflection pulse 755 is
applied to the scan electrode 310R1 adjacent to the electron
emission element connected to the scan electrode 310R2. The voltage
of the deflection pulse is taken as Vdef=-V.sub.R3. In this manner,
by setting the voltage of the deflection electrode 315 suitably, a
voltage relation among the deflection electrode 315, the contact
electrode 55, and the top electrode 11 is optimized, thereby making
it possible to obtain a higher beam deflection effect.
[0145] As evident from FIG. 10, an electron lens that deflects an
electron beam trajectory is affected by the voltage of phosphor
screen, the voltage of the deflection electrode, and the voltage of
the top electrode. The voltage between the top electrode and the
defection electrode at the electron emission time is (Vs-Vns) in
the driving method of FIG. 25, and is (Vs-Vdef) in the driving
method of FIG. 26. As a result of having performed an electron
trajectory simulation, it is shown that the larger (Vs-Vdef) is,
the larger the beam deflection amount is. Consequently, when the
beam deflection amount is desired to be increased, it is preferable
to make the absolute value of (Vs-Vdef) larger than the absolute
value of (Vs-Vns). Further, as the more preferred embodiment, the
voltage -V.sub.R3 of the deflection pulse 755 is set equal to the
voltage -V.sub.R2 of the reverse pulse 754. When the setting is
made in this manner, the drive circuit is simplified, and this is
more preferable.
[0146] As more preferable mode of the present embodiment, the
relation between the phosphor region 144 and the electron emission
region 35 will be described. As described above, since the phosphor
is a place in which the positive ion is easily generated, when the
phosphor region 144 is disposed so as not to be mutually superposed
with the electron emission region 35 in a projected plane, the
generation of the positive ion and its irradiation to the electron
emission region can be further reduced, and therefore, this is more
preferable. That is, in FIG. 10, designing such that d3>0 and
d4>0 is more preferable. The condition [d3>0] is a condition
in which the phosphor region 144 corresponding to the electron
emission region is not superposed with the electron emission
region, and the condition [d4>0] is a condition in which the
adjacent phosphor region 144 is not superposed with the electron
emission region.
[0147] In the present embodiment, the deflection electrode 315 uses
the same material as the scan line 310 (that is, the busline
electrode 32), and is patterned simultaneously in the same
photolithographic processes. By so doing, even when the deflection
electrode is introduced, it can be fabricated by the same
fabrication process as the conventional art without increasing the
number of photomasks, and this is preferable.
Third Embodiment
[0148] A third embodiment of the present invention will be
described with reference to FIGS. 27 and 28A-28B. FIG. 27 is a top
plan view of a cathode plate 601 constituting a display panel 100
used in the present embodiment. FIGS. 28A and 28B are cross section
of the cathode plate 601, FIG. 28A is a cross section along line
A-B of FIG. 27, and FIG. 28B shows a cross section along line C-D.
When comparing the third embodiment with the second embodiment
(FIGS. 13 and 14A-14B), the shape of a contact electrode 55 is
different in the present embodiment. While the contact electrode 55
has a branch-shaped protrusion extending along the longer side of
the electron emission region 35 in FIG. 13, the protrusion is not
available in the present embodiment (FIG. 27).
[0149] As evident from FIG. 28B, a top electrode 11 is formed
almost entirely on the surface except for a scan electrode 310
(that is, a busline electrode 32) and a deflection electrode 315.
Since the film thickness (0.1 .mu.m in the present embodiment) of
the contact electrode 55 is 1/100 of the film thickness of 10 .mu.m
of a deflection electrode 315, the shape of the contact electrode
is hardly affected by electric field distribution near an electron
emission region 35. Consequently, even by the electrode shape of
FIGS. 27 and 28, the beam deflection effects similar to the
preceding embodiments can be obtained.
[0150] In the present embodiment (FIG. 27), since the shape of the
contact electrode is simple, it has the advantage of being easily
manufactured. In particular, when the contact electrode is
patterned, there is no need for high accuracy in mask alignment in
a lateral direction, it can be easily fabricated. On the other
hand, the contact electrode shape of FIG. 13 has the advantages of
being high in current feeding ability and increasing electron
emission efficiency and reliability of thin film electron emitter.
This will be described with reference to FIGS. 29A and 29B. The
contact electrode 55 has a role of electrically connecting the scan
line 310 (which is formed of a busline electrode 32 in the present
embodiment) and the top electrode 11. In the thin film electron
emitter, though the entire electron emission region 35 is required
to be fed with the current, since the thickness of the top
electrode 11 is thin such as approximately 10 nm or less, the
resistance is high. Hence, the current is fed through the contact
electrode 55 which is approximately 100 nm in film thickness and
is, therefore, small in electrical resistance.
[0151] The relation between the contact electrode shape and the
current feeding ability will be described with reference to FIGS.
29A and 29B. FIGS. 29A and 29B schematically show the disposition
of the electron emission region 35, the contact electrode 55, and
the scan electrode 310 (formed of the busline electrode 32 in the
present embodiment). FIG. 29A corresponds to the embodiment of FIG.
27, and FIG. 29B corresponds to the embodiment of FIG. 13.
[0152] In the contact electrode shape of FIG. 29A, since the
current is fed from a single side 871 only of the electron emission
region 35, the current builds up in the single side 871, and
density of the current that flows to the top electrode 11 is
relatively high. On the other hand, in the contact electrode shape
of FIG. 29B, since the current is fed from two sides 871 and 872 of
the electron emission region 35, the current is scattered. Hence,
the density of the current that flows to the top electrode 11 is
reduced. Accordingly, the resistance value required for the top
electrode can be higher. Hence, it is possible to make the top
electrode film thickness thinner. When the top electrode is made
thinner, inelastic scattering of hot electron inside the top
electrode is reduced, so that the electron emission efficiency is
increased. Further, as the current is scattered, reliability of the
connection between the contact electrode and the top electrode is
improved.
[0153] In the color image display apparatus, in many cases, the
sub-pixels of red color, green color, and blue color are disposed
in the lateral direction, thereby constituting one pixel. Since one
pixel is approximately square, the shape of each sub-pixel is
normally vertically long. In response to this, the shape of the
electron emission region 35 corresponding to each sub pixel is also
made vertically long. For this reason, in the color image display
apparatus, a ratio of b0/a0 of FIG. 29 is normally larger than 1,
and it is typically 2 to 3. Hence, in FIG. 29(a), the current
builds up in the shorter side of the electron emission region 35.
In FIG. 29(b), since the current is fed also from the longer side
of the length b0, the current is scattered. In this manner, when
the contact electrode 55 is disposed along the longer side of the
electron emission region 35, the current density that flows in the
top electrode is reduced, and this is more preferable.
Fourth Embodiment
[0154] A fourth embodiment of the present invention will be
described with reference to FIG. 31. The present embodiment uses a
thin film electron emitter as an electron emission element. FIG. 31
is a top plan view of the cathode plate 601 constituting the
display panel 100, and shows main constituent components only. FIG.
31 corresponds to FIG. 11 of the above described embodiment. In
FIG. 31, a scan line 310, a contact electrode 55, and an electron
emission region 35 of each electron emission element 301 only are
described from among the constituent components constituting a
cathode plate 601. An electron emission region 35-2 is electrically
connected to a scan line 310-2 via the contact electrode 55.
[0155] In the present embodiment, the film thickness of the scan
line 310 is taken as 6 .mu.m in thickness, so that a height of the
scan line 310 is made sufficiently higher than a height of a top
electrode, and the scan line 310 is allowed to perform also the
function as a deflection electrode. As shown in FIG. 31, an
electron emission region 35 is disposed so as not to include a
center line G-H 430 of the distance of the inner edges between
adjacent scan lines. By so doing, the electron emitted from the
electron emission region is vertically deflected (in the
figure).
[0156] Here, the "height" of the electrode is a value defined by
FIG. 30 as described above. That is, similarly to FIG. 30A, when a
substrate 14 is directly formed with a deflection electrode 315,
its film thickness becomes a height h0. Further, similarly to FIG.
30B, when the deflection electrode 315 is formed on a dielectric
layer 385, a length (h0 in the figure) up to the highest position
of the deflection electrode 315 defines the height. In FIGS. 30A
and 30B, while the height of the deflection electrode 315 is shown,
the height of the scan line 310 is defined by rereading the
deflection electrode 315 into the scan line 310 in FIGS. 30A and
30B. Even in the case such as FIG. 30B, the height h0 mainly
controls electron lens characteristics.
[0157] In the present embodiment, without providing a protrusion of
the deflection electrode 315 such as FIG. 11 in the scan line 310,
the height of the scan line 310 itself is utilized so as to allow
it to have the function of the deflection electrode. When compared
with the second embodiment, the wiring pattern is simple, and
therefore, an advantage is afforded that the deflection electrode
is easy to manufacture.
[0158] On the other hand, in the second embodiment, as shown in
FIG. 11, the deflection electrode 315 is periodically disposed
along the axis in parallel with the scan line 310. That is, while
the deflection electrode 315 is periodically disposed, this
repeating direction is in parallel with the scan line 310. As a
result, the electron beam, as shown in FIG. 10, is deflected in the
direction parallel to the scan line 310. The main advantages of
allowing the beam to deflect into this direction have two points as
follows.
[0159] The first point is that a distance (period) between the
adjacent deflection electrodes 315 are short. The shorter the
distance between the deflection electrodes 315 is, the more
increased the effect of the electron lens is, and therefore, the
deflection amount of the electron beam is increased. Hence, the
effect of ion irradiation can be reduced. As described above, in
the color image display apparatus, since there are many cases where
the sub-pixel is disposed in the horizontal direction, it is more
preferable that the deflection electrode 315 is periodically
disposed along the axis in parallel with the scan line 310 as shown
in FIG. 11, so that the distance between the deflection electrodes
is made shorter.
[0160] The second point is that the electron beam is deflected in
the direction parallel to the spacer 60, and this is preferable in
preventing an electrical charging of the spacer. When the spacer 60
is charged, the electric field inside the display panel is
distorted, and this sometimes causes the electron beam to deviate
from a desired path or route, thereby adversely affecting the
display image. If the deflection direction of the electron beam is
in a direction parallel to the spacer 60, the spacer 60 can be
prevented from being charged. In a typical display panel, as shown
in FIG. 13, the spacer 60 is disposed in the direction parallel to
the scan line 310 (busline electrodes 32 and 34). Therefore,
similarly to FIG. 11, the deflection electrode 315 is periodically
disposed along the axis in parallel to the scan line 310, so that
the direction of the beam deflection is in the direction parallel
to the spacer 60.
Fifth Embodiment
[0161] A fifth embodiment of the present invention will be
described with reference to FIGS. 32 and 33. The fifth embodiment
uses a thin film electron emitter as an electron emission element.
FIG. 32 is a cross section of a part of a display panel 100 used
for an image display apparatus of the present embodiment. Further,
FIG. 33 is a corresponding top plan view. A cross section along A-B
of FIG. 33 is FIG. 32. In FIG. 32, with respect to an electron
emission element 301 constituted by the thin film electron emitter,
its electron emission region 35 only is described. A description of
the internal structure of the thin film electron emitter, that is,
the internal structure such as the top electrode 11, the electron
acceleration layer 12, and the base electrode 13, and a detailed
wiring structure of an interlayer insulating film, a data line and
so on are omitted. The detailed structures of these constituent
components are the same as the second embodiment.
[0162] A top plan view of FIG. 33 is a schematic top plan view
showing a positional relation among a scan line 310, a contact
electrode 55, an electron emission region 35, and a shield
electrode 371, and the illustration of other constituent components
are omitted. In FIG. 32, the top electrode 11 of the electron
emission element 301 which takes the electron emission region 35 as
a constituent component is electrically connected to the scan line
310 via the contact electrode 55. The height of the scan line 310
is 10 .mu.m. On the scan line 310, a dielectric layer 372 is
disposed, and upon thereof, the shield electrode 371 is disposed.
The shield electrode 371 protrudes immediately above the electron
emission region 35, and its protrusion length L2 is 50 .mu.m. The
film thickness T2 of the dielectric layer 372 is 100 .mu.m. A
distance L0 between the cathode plate 601 and the phosphor plate
602 was taken as 3 mm. A phosphor screen voltage Va was taken as 10
KV. The trajectory of the electron beam emitted from the electron
emission region 35 under this condition is an electron trajectory
921 which is obtained by simulation. The electron beam emitted from
the electron emission region 35 is deflected by 400 .mu.m when
reaching the phosphor plate 602, and bombards or irradiates the
phosphor 114 to excite the phosphor to emit light.
[0163] The characteristic of the present invention is that the
electron emission region 35 is covered with the shield electrode
371 in the projecting plane projecting the shield electrode 371 and
the electron emission region 35 in the same plane. That is, the
protrusion length L2 of the shield electrode 371 is sufficiently
large to cover the entire electron emission region 35. By so doing,
even when ion generated close to the phosphor plate 602 inside the
panel bombards or irradiates the cathode plate 601, the ion is
shielded by the shield electrode 371 and does not reach the
electron emission region 35. Hence, the thin film electron emitter
constituting the electron emission element 301 is not
deteriorated.
[0164] The display panel 100 of the present embodiment is
fabricated as follows. It is fabricated by the same process as the
second embodiment up to the process of FIGS. 21A-21C. Next, it is
coated with photosensitive glass, and is patterned, thereby to form
the dielectric layer 372. After that, by the processes of FIGS.
22A-22C and 23A-23C, the top electrode 11 is deposited with film,
thereby to fabricate the cathode plate 601. When it is combined
with the phosphor plate 602 to assemble the display panel 100, the
shield electrode 371 of slit form is inserted. At this time, the
terminals of the shield electrode 371 are taken out from the
display panel. The drive waveform of the image display apparatus of
the present embodiment uses a waveform of FIG. 25. The shield
electrode 371 is set to 0V.
[0165] In the foregoing, the invention made by the inventors of the
present invention has been concretely described based on the
embodiments. However, it is needless to say that the present
invention is not limited to the foregoing embodiments and various
modifications and alterations can be made within the scope of the
present invention.
* * * * *